Morris "Moe" Berg, this film tells us, was an enigma, and he had reason to be during his life; he was Jewish in a time when one didn't loudly declare it, a "lifelong bachelor" who zealously guarded his privacy, and an academic achiever who spent his youth as a professional baseball player before undertaking missions for the OSS during World War II. It's a shame that the filmmakers aren't more interested in cracking that shell in order to see what's underneath.

Screenwriter Robert Rodat takes a fair amount of liberties with the story, starting by moving a 1934 all-star tour of Japan to 1936, when he was a backup catcher for the Boston Red Sox. While there, Berg (Paul Rudd) meets a Japanese historian (Hiroyuki Sanada) who opines that their countries will inevitably go to war and then surreptitiously makes his way to the roof of one of Tokyo's tallest buildings to get footage of the city's layout, including the naval yards. After Pearl Harbor, he contacts a friend from Princeton who works in the State Department. There's a place for smart, physically capable who speak nearly a dozen languages like Berg in the Office of Strategic Services, and though he's initially placed on a desk, he's given a mission to accompany Dutch physicist Samuel Goudsmit (Paul Giamatti) to Rome to learn what progress Werner Heisenberg (Mark Strong) has made as the head of Germany's nuclear program - a mission that will take him to Zurich, where Heisenberg frequently visits colleague Paul Scherrer (Tom Wilkinson), tasked with assassinating Heisenberg if necessary.

You could cut about half of that out and still have a story that sounds too good to be true, but the trick is to tell it well. The basics of Berg's story are enough to capture the imagination, but the filmmakers seem a bit too willing to just let the audience fill in the details rather than stitch it together into a particular story. The through-line they do find is speculative, positing that his skill and passion for secrecy comes from being a closeted bisexual man in that era. It's entirely possible - Berg's ability to keep a secret might just have been good enough to leave no trace even when it might have made him a queer icon in the present - but it's a direction that can only have a limited payoff. The way they loudly tap-dance around his sexuality is right out of the era's playbook - shouted slurs rebutted by a heterosexual sex scene, assertions of open-mindedness only backed up by hints - so it's a kind of half-hearted commitment to the theme.

It's disappointing that what they actually show seems so bland, too; writer Robert Rodat seems to assemble a checklist of anecdotes that director David Lewin cannot often convert into exciting scenes. Scenes may not be flat all the way through, but will often end that way and have the important things that happened dropped. Even the centerpiece battlefield action is drab, feeling like an imitation of action movies that truly invest in getting to the other side of the shooting gallery. The movie is arguably most alive during its brief old-time baseball scenes, enough that one wonders how they could have it more central, maybe taking a broader look at Berg's life and comparing his rise and fall on the diamond with his life afterward.

Star Paul Rudd doesn't often take this dramatic a role, and he does seem most confident when he can be funny or charming. There sometimes doesn't seem to be anything underneath his more ambiguous moments besides being mysterious. He's surrounded by an impressive, capable cast, enough to enliven every scene: Hiroyuki Sanada is magnetic as the friend he makes in Japan, Jeff Daniels makes a reassuringly capable stern authority figure, and Paul Giamatti is more reined in than usual but still passionate as the pacifistic scientist partnered with Berg on his mission. The trouble is that they are all playing fairly isolated characters, only fitting into one corner of Berg's life. The closest thing to a relationship that drives the movie involves Sienna Miller as Berg's girlfriend, and that's about them not marrying while he's still in Boston.

It's a neat story and a good cast for it; it just never becomes as exciting as it is intriguing. It's never bad enough to truly dislike, but at no point does it live up to its potential. There's supposedly a documentary on the way from the makers of "The Life and Times of Hank Greenberg" which may tell Berg's story better, but in the meantime, this is serviceable but disappointing.